碳纳米管的非破坏性功能化及其应用

发布时间：2018-05-18 23:31

  本文选题：碳纳米管 + 功能化　； 参考：《华东师范大学》2015年硕士论文

【摘要】：经过二十多年的发展,碳纳米管(Carbon Nanotubes, CNTs)领域己进入到应用化研究阶段,制备具有实用价值的功能性CNTs材料是目前的主要研究方向。很多实际应用要求CNTs同时具备两个条件：结构完整和功能化。因此,非破坏性的高效功能化是研究人员持续追求的一个目标。共价功能化通过CNTs和化学物质反应形成共价键,能达到高功能化程度,但唯一的缺点是反应物攻击CNTs管壁的C=C键,破坏CNTs的共轭结构。非共价功能化能在保持CNTs原有的结构的情况下引入官能团,但由于是基于CNTs与修饰剂分子的弱相互作用,其功能化程度一般不高,复合物也不稳定。为了实现CNTs的非破坏性高效功能化及其相关应用,本论文做了以下工作。1.高分子对CNTs的非共价缠绕及其对染料分子的增强吸附(1)利用聚苯乙烯磺酸钠(PSS)对CNTs的非共价缠绕,实现了对CNTs的非破坏性高效功能化,并研究了CNTs和PSS的相互作用。PSS具有柔性的分子链、丰富的阴离子基团和芳香侧基,能通过非共价的缠绕为CNTs同时引入大量的负电荷和π电子。本实验采用简单的超声分散和加热搅拌的方法来制备CNT/PSS复合材料；产物的胶体分散性、紫外可见吸收光谱、红外光谱(IR)、场发射扫描电镜(FESEM)和热重分析等结果证明了有大量的PSS修饰在了CNTs上。通过X一光电子能谱(XPS)对CNTs、PSS和CNT/PSS的化学状态进行了表征,发现PSS的芳香侧基和CNTs表面的共轭系统通过π-π作用结合在一起;同时PSS苯环上的强吸电子取代基磺酸基能够利用这种π-π作用从CNTs上吸取电子,增加了磺基的电子云密度。据此,我们首次提出了CNTs和高分子可能通过“π-π电子供受”作用结合在一起的非共价修饰机理,而非简单的π-π作用。(2)应用CNT/PSS实现了对染料分子的增强吸附,并研究了吸附机理。以亚甲基蓝(MB)为模型吸附质,使用吸附等温线和吸附动力学对比研究了CNTs和CNT/PSS的吸附行为。结果发现,与未处理CNTs相比,CNT/PSS对MB的吸附速率和吸附容量却有大大的提高,其中吸附容量为原来的2倍多,达到了100 mg/g,且在实验条件下CNT/PSS用作吸附剂仅需3 min就能接近吸附平衡(CNTs需要10 min)。为了研究增强吸附的机理,使用XPS对吸附相互作用进行了表征。首先精确的定位了吸附位点(活性官能团),发现MB除了通过芳香环与CNTs管壁的π-π作用被吸附之外,还通过一端的二甲胺基被CNT/PSS表面的磺酸基静电吸引；然后计算出了静电作用和π-π作用对吸附容量的相对贡献是2：1；并从分子构型等角度对静电吸附的优势给予了合理解释,最后使用理论计算证实了分析结果。2.六价铁Fe(VI)用作CNTs的氧化剂及CNTs非破坏性共价功能化的实现首次使用高铁酸钾K2FeⅥO4作为CNTs的氧化剂,发现以浓硫酸为反应介质时,Fe(Ⅵ)可在温和的反应条件(60℃)下实现CNTs的快速(3h)羧基化,氧化效果通过了胶体分散性和IR的定性表征。这种新型的氧化方法具有反应条件温和、高效、不产生污染物(唯一副产物是Fe3+)等优点。更重要的是,该氧化手段不会破坏CNTs的共轭结构。用Raman光谱定量测试了氧化前后CNTs的缺陷程度,发现Fe(Ⅵ)的氧化不会在CNTs表面引入新的缺陷。结合Raman光谱、FESEM和XPS数据,我们分析了氧化机理,结果表明：Fe(Ⅵ)对CNTs的氧化反应选择性的发生在原有的sp3-C上,而不会破坏C=C键。CNTs外表面的sp3-C于3 h之内被全部氧化,此时反应结束,延长反应至6 h并不会增加反应程度。由于非破坏性的氧化既引入了含氧官能团,又不破坏CNTs的结构,氧化的CNTs的产率超过了100wt%。用当前盛行的高效但具有破坏性的混酸(HNO3/H2SO4)氧化的结果与Fe(Ⅵ)氧化的结果进行了对比,进一步说明了Fe(Ⅵ)对CNTs的缺陷专一性/非破坏性的氧化机理。这种非破坏性氧化为CNTs的非破坏性共价功能化奠定了基础。
[Abstract]:After more than 20 years of development, the Carbon Nanotubes (CNTs) field has entered the applied research stage. The preparation of functional CNTs materials with practical value is the main research direction. Many practical applications require that CNTs has two conditions at the same time: structural finishing and functionalization. Therefore, non destructive and efficient functionalization. It is a goal that researchers continue to pursue. Covalently functionalized through the reaction of CNTs and chemicals to form covalent bonds to achieve a high degree of function, but the only disadvantage is that the reactants attack the C=C key of the CNTs tube wall and destroy the conjugate structure of the CNTs. The non covalent functionalization can introduce functional groups in the case of maintaining the original structure of CNTs, but Therefore, based on the weak interaction of CNTs and modifier molecules, the degree of functionalization is generally low and the complex is not stable. In order to realize the nondestructive and efficient functionalization of CNTs and its related applications, the following work has been done by.1. polymer on the non covalent entanglement of CNTs and the enhanced adsorption of the dye molecules (1) using polystyrene sulfonic acid. The non covalent entanglement of CNTs by sodium (PSS) realizes non destructive and efficient functionalization of CNTs, and studies the interaction of CNTs and PSS with a flexible molecular chain, rich anionic groups and aromatic side groups. A large number of negative charges and pion electrons can be introduced into CNTs by non covalent entanglement, and a simple ultrasonic dispersion is used in this experiment. The CNT/PSS composite was prepared by the method of heating and stirring. The colloid dispersion, UV visible absorption spectrum, infrared spectrum (IR), field emission scanning electron microscopy (FESEM) and thermogravimetric analysis showed that a large number of PSS modification was on CNTs. The chemical state of CNTs, PSS and CNT/PSS was characterized by X photoelectron spectroscopy (XPS). It is found that the aromatic side of the PSS and the conjugated system on the surface of the CNTs are combined together by the effect of pi - pi; at the same time, the strong electron absorption substituent on the PSS benzene ring can use this pi - pi effect to absorb electrons from the CNTs and increase the electron cloud density of the sulfonyl group. Accordingly, we have first proposed that CNTs and polymer may be subjected to "pi - pi electron donor". The mechanism of non covalent modification, not simple Pi Pi action, was combined. (2) the adsorption mechanism of dye molecules was enhanced by CNT/PSS, and the adsorption mechanism was studied. The adsorption isotherm and adsorption kinetics were studied with methylene blue (MB), and the adsorption behavior of CNTs and CNT/PSS was studied by adsorption isotherm and adsorption kinetics. Compared with CNTs, the adsorption rate and adsorption capacity of MB were greatly improved, in which the adsorption capacity was 2 times more than that of the original, and the adsorption capacity reached 100 mg/g. And under the experimental conditions, CNT/PSS was used as an adsorbent only 3 min to close the adsorption equilibrium (CNTs need 10 min). In order to study the mechanism of adsorption enhancement, the adsorption interaction was used. Firstly, the adsorption site (active functional group) was accurately located, and it was found that MB was attracted by the sulfonic acid based electrostatic force on the surface of CNT/PSS by the two methylamine at one end by the adsorption of the pion - pi action of the aromatic ring and the wall of the CNTs tube, and then calculated the relative contribution of the electrostatic and PI - pi action to the adsorption capacity of 2:1. The advantages of electrostatic adsorption were explained reasonably from the angle of molecular configuration. Finally, the theoretical calculation proved that.2. six valence iron Fe (VI) was used as oxidant for CNTs and the non destructive covalent functionalization of CNTs, the first use of potassium ferrate K2Fe VI O4 as an oxidant for CNTs, and found that when concentrated sulfuric acid was the reaction medium, Fe was found. (VI) the rapid (3H) carboxylation of CNTs can be realized at a mild reaction condition (60 degrees C). The effect of oxidation is characterized by the colloid dispersion and the qualitative characterization of IR. This new oxidation method has the advantages of mild reaction conditions, high efficiency, no pollutants (the only by-product is Fe3+), and more importantly, the oxidation method will not destroy the conjugation of CNTs. Structure. The defect degree of CNTs before and after oxidation was measured by Raman spectrum. It was found that the oxidation of Fe (VI) did not introduce a new defect on the surface of CNTs. We analyzed the oxidation mechanism by combining the Raman spectrum, FESEM and XPS data. The results showed that the selectivity of Fe (VI) on the CNTs oxidation reaction occurred on the original sp3-C, not the C=C bond.CN. The sp3-C on the outer surface of the Ts is completely oxidized within 3 h, at the time the reaction ends and the reaction is extended to 6 h and does not increase the degree of reaction. As the non destructive oxidation both introduces oxygen containing functional groups and does not destroy the structure of CNTs, the yield of the oxidized CNTs exceeds the current highly effective but destructive mixed acid (HNO3/H2SO4) oxygen prevailing in 100wt%. with the current 100wt%.. The results are compared with the results of Fe (VI) oxidation, which further illustrates the specific / nondestructive oxidation mechanism of Fe (VI) to CNTs. This nondestructive oxidation lays the foundation for the non destructive covalent functionalization of CNTs.
【学位授予单位】：华东师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ127.11;TB383.1

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